For this learning playdate, one of the subjects was Geography. The kids learnt to identify Malaysia on a globe. First the kids were shown were Malaysia was on the globe. They the globe was spun and they had to find Malaysia. I was surprised that E at 3 years of age could identify Malaysia on the globe after learning it just once.
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| Learning about the various states in the Malaysia and their corresponding flags |
For the Science activity, we did paper chromatography and tried to separate the ink pigments to its various colours.
Procedure
- Cut several coffee filters into long strips. (We used paper kitchen towels, but found that it was rather fragile. Coffee filter would be better, but we don't know where to purchase them in Malaysia.
- Place a dot of ink near the bottom of each strip. (We used magic colours / marker pens)
- Add water to the glass / cup until it reaches the bottom of the paper strip just below the ink dot. Ensure that the ink stays above the water and the paper stays in the water.
- Watch how the ink spreads up the paper.
- Try with different colours and watch the results.
Explanation:
Because molecules in ink and other mixtures have different characteristics (such as size and solubility), they travel at different speeds when pulled along a piece of paper by a solvent (in this case, water). For example, black ink contains several colours. When the water flows through a word written in black, the molecules of each one of the colours behave differently, resulting in a sort of “rainbow” effect.
Many common inks are water soluble and spread apart into the component dyes using water as a solvent. If the ink you are testing does not spread out using water, it may be “permanent” ink. In such cases, you will have to use a different solvent such as rubbing alcohol.
We didn't really see much difference in the colours from the blue and red magic pen that the boys used. Will try black marker pen the next time. Now, where can I find coffee filter paper in the Klang Valley?
I found the following tips from this website:
- Coffee filter is recommended for this experiment because it is cheap and can be purchased easily. The experiment works even better with filter paper or chromatography paper, but these are more expensive. Black pens are recommended because they usually have many different dyes in their ink. Students should be encouraged to try markers of different colors or food coloring (the green food coloring works well). Do not be disappointed if the marker does not produce a dramatic separation pattern.
- Water rises up the coffee filter because of a phenomenon called capillary action. It is the same action which a tree uses to soak water up its trunk and its branches. After all, coffee filter is made from trees! One can mimic a tree using a thick paper towel and rolling it as a trunk.
- The role of the water and the rubbing alcohol in this experiment is that of a carrying liquid, because these liquids carry the ink up the coffee filter. The technical term for this is an eluant.
- Students are expected to make the following observations:
- marks made from the same pen always produce the same separation pattern, i.e., the different colors are in the same order after the separation. The size of the original dot on the paper has no effect on the separation pattern, although the separation is better defined if the dot is smaller.
- different brands of pen produce different separation patterns.
- different carrying liquids produce different separation patterns with the same pen.
- Students should be shown that different pens from the same batch (same brand and same model) produce the same separation pattern.
- The separation patterns produced by different brands of pen and different carrying liquids are governed by several factors:
- The composition of the ink. Different companies use different dyes to make their ink. Some are doing it to produce special physical or visual effects, some are doing it so they cannot be accused of copying other people’s product.
- The solubility of each component dye in the carrying liquid. If the dye is not soluble in the carrying liquid, it cannot be carried up the paper. This is the case of the permanent ink with water as the carrying liquid. Since the permanent ink is not soluble in water (hence the term :"permanent"), the mark stays in the starting place. Since most permanent ink are soluble somewhat in organic solvents, one can get it to produce a pattern using rubbing alcohol as the carrying liquid.Typically, the most soluble dye will move up the paper the most and the least soluble dye will move up the least. If a dye is very soluble in the carrying liquid, it will follow the top of the water level up the paper closely. Try the experiment with a washable marker.
- The extent to which the ink clings to the paper. A dye which is strongly attached to the paper will not move up the paper much.
- The length of the paper. The separation of the different dyes along the paper increases if the carrying liquid is allowed to carry the ink up a longer distance. At the beginning of the experiment, the colors are still bundled together. As the carrying liquid moves up the paper, the separation becomes more and more complete. Note, however, that the order of the colors does not change with the distance traveled.
- The teacher can take one of the markers which the students have used and use it to put a mark on a coffee filter. Give this to the students as an unknown and ask the students to identify which marker was used to make the mark. The students should be able to device the following procedure:
- Take the paper with the unknown and run the paper chromatography experiment in exactly the same way as with the other markers.
- Observe the separation pattern produced by the unknown, and compare it with the patterns produced by the known markers.
- The marker which produces the same pattern as the unknown is the origin of the unknown.
- To obtain a better confirmation, you can perform a chromatography of the unknown and of one (or many) known marker, simultaneously, on the same paper.
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